Well, this thread has me thinking, as neither of our heads has vented loops
in the intake line, and the aft head is distinctly under the waterline (fwd
isn't except on sharp port tack).

So, if I understand vented loops properly, suction gets air, rather than
water, thus preventing siphoning. So, how do you suck in the supply water
if the supply line is vented???

L8R

Skip, scratching his head, pardon the expression (solidly asking pardon for
the other - inferred solid - expression)

--
Morgan 461 #2
SV Flying Pig KI4MPC
http://tinyurl.com/384p2 The vessel as Tehamana, as we bought her

"Twenty years from now you will be more disappointed by the things you
didn't do than by the ones you did do. So throw off the bowlines. Sail
away from the safe harbor. Catch the trade winds in your sails. Explore.
Dream. Discover." - Mark Twain

On Mon, 12 Dec 2005 20:49:04 +0200, Mike the Spamkiller
wrote:


We usually open the toilet intake seacock when we get to our boat and
have it open as long as we are under way. Have reconsidered that
practice since then.

I draw lake water to flush through a seacock topped with a T-valve.
Above the T-valve (to the toilet and just a shave below the waterline)
is the drain hose to the sink. I leave the seacock SHUT unless I or
someone aboard is using the toilet. I have the option of emptying the
sink into the lake or if there's something noxious in the sink, I can
drain it into the toilet and then to the holding tank. This year, I
vented the loop as well. Everything is double-clamped. We've had two
boats sink at dock in a club of 220 in the last five years due to this
sort of issue...and it's completely avoidable.

The only seacock open when underway is the freshwater intake for the
motor. All others are shut unless in use. All others have bungs tied
to the seacock handles.

If you think of them not as seacocks but as "large holes in the bottom
of the boat capable of letting in dozens of gallons a minute" I find
it focuses the mind wonderfully.

R.

Peggie Hall wrote:
phasmatis wrote:

The evening before the boat sank a large power craft powered at speed
through the Marina and created a very large bow wave, the only
explanation as to the cause that has been offered is that the bow wave
caused the toilet to overflow and created a syphoning effect which in
turn filled the yacht with water.
Anyone heard of this before?



Many times...but it's unlikely that the large wake had anything to do
with it. Head seacocks left open when no one is aboard are the leading
causes of boats sinking in their slips.

His toilet is below the waterline...I'd bet real money that a) he's
never installed a vented loop in the head intake...and b) he never
bothers to close the head intake (nor the discharge either) seacock when
he leaves the boat, foolishly relying on the wet/dry valve in the toilet
to prevent water from overflowing the bowl. Either the valve failed
(very common), or the toilet was left in the wet mode. It only takes a
few hours for enough water to flood the boat via the toilet to sink it.

So when I heard this last week here I realized I am one of the fools who
trusted their wet/dry valve and left the seacock open on the head
intake. I spent the last week trying to reassure myself that the wet/dry
valve has held up for a good year now (since I rebuilt the toilet!), but
I was nervous. So yesterday I finally got to the boat and closed the
seacock. Everything was dry as a bone on board. Just lucky I guess.

But my question is, I don't have a vented loop in the line, a vented
loop would be hardish to install with the layout I have. Should I put
one in or not, assuming I never again leave the seacock open?


--
Stephen

-------

For any proposition there is always some sufficiently narrow
interpretation of its terms, such that it turns out true, and
some sufficiently wide interpretation such that it turns out
false...concept stretching will refute *any* statement, and will
leave no true statement whatsoever.
-- Imre Lakatos

phasmatis wrote:
A friend of mine has a Beneteau 345 moored in Corfu, it was due to be
lifted out for the winter this morning but unfortunately he had a phone
call from the Marina to say his boat had sank! The boat was stern on to
the pontoon and it was only the ropes holding the stern end out of the
water. There are no other boats on the pontoon as they have already
been lifted out.

The boat has now been pumped out and is afloat again and on inspection
there is no obvious reason why the boat would take on so much water to
sink the boat in a 12 hour period since it was last viewed.

The evening before the boat sank a large power craft powered at speed
through the Marina and created a very large bow wave, the only
explanation as to the cause that has been offered is that the bow wave
caused the toilet to overflow and created a syphoning effect which in
turn filled the yacht with water.

Anyone heard of this before?

Yup, my cousins bilge pump started syphoning and sank his boat.

In Gtpnf.94832$ki.57113@pd7tw2no Gary writes:

phasmatis wrote:
A friend of mine has a Beneteau 345 moored in Corfu, it was due to be
lifted out for the winter this morning but unfortunately he had a phone
call from the Marina to say his boat had sank! The boat was stern on to
the pontoon and it was only the ropes holding the stern end out of the
water. There are no other boats on the pontoon as they have already
been lifted out.

The boat has now been pumped out and is afloat again and on inspection
there is no obvious reason why the boat would take on so much water to
sink the boat in a 12 hour period since it was last viewed.

The evening before the boat sank a large power craft powered at speed
through the Marina and created a very large bow wave, the only
explanation as to the cause that has been offered is that the bow wave
caused the toilet to overflow and created a syphoning effect which in
turn filled the yacht with water.

Anyone heard of this before?

Yup, my cousins bilge pump started syphoning and sank his boat.

My neighbour in the club marina had a 30 footer, where the builder was
being smart and had joined the bilge pump and kitchen sink outlet. If
you left the kitchen sink plug on after you had pumped the bilge, you
had a perfect siphon. Of course it happened once. He was lucky that
someone noticed that hes freeboard (usually about six inches higher than
mine, was about a foot lower than mine and came to the rescue.

Another case was with the toalet pump in another boat. So if you make a
sifon, once it will work. Just wait long enough.

- Lauri Tarkkonen

Lauri Tarkkonen wrote:
My neighbour in the club marina had a 30 footer, where the builder was
being smart and had joined the bilge pump and kitchen sink outlet. If
you left the kitchen sink plug on after you had pumped the bilge, you
had a perfect siphon.

You're saying that bilge pump discharged BELOW the waterline???? What
WAS the builder thinking??? Otoh, I had a consulting job last year on a
70' trawler on which both the gray water and the black water tank vents
terminated in charcoal canisters in the engine room, right next to a
propane furnace. So anything is possible.

Of course it happened once. He was lucky that
someone noticed that hes freeboard (usually about six inches higher than
mine, was about a foot lower than mine and came to the rescue.

Another case was with the toalet pump in another boat. So if you make a
sifon, once it will work. Just wait long enough.

But you CAN'T create a siphon if you close the bloomin' seacock! No
matter how inaccessible and inconvenient that may be, it's a whole LOT
easier and more convenient than drying out your boat after it's sunk in
its slip.
--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://www.seaworthy.com/store/custo...0&cat=6&page=1
http://shop.sailboatowners.com/books...ku=90&cat=1304

Gary wrote:
Yup, my cousins bilge pump started syphoning and sank his boat.

I don' TEEENK that's what happened...for a couple of reasons: bilge
pumps don't bring water INTO the boat, they remove water FROM the
boat...and the thru-hulls for bilge pumps are above the waterline. So
unless there was already enough water in the boat to put the bilge pump
thru-hull under water, there's no way that a siphon can start in a bilge
pump line.

The water that sank your cousin's boat had to be coming in somewhere
else...and either the bilge pumps clogged and failed, or they kept
pumping till they drained the batteries and died...allowing the boat to
fill up and sink. Or, the water was coming in faster than the bilge
pumps could keep up with it. Or any combination/all of the above.

--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://www.seaworthy.com/store/custo...0&cat=6&page=1
http://shop.sailboatowners.com/books...ku=90&cat=1304

Peggie,

Trying to tell people to install vented loops is like trying to get them to
close seacocks when they leave the boat for extended periods. Ain't gonna
happen.

When you tell people they should close all the through hulls prior to
leaving they say that is not what they are for, or that would take to long,
or don't you trust your hoses, or I can't get too my through hulls,,,,and
that is why most boats sink at the dock.

You should see the looks I get from the yard when I tell them the ignition
key is hanging on the closed raw water engine intake and they will need to
open the intake when getting the key to start the engine.

B

"Peggie Hall" wrote in message
...
Gary wrote:
Yup, my cousins bilge pump started syphoning and sank his boat.

I don' TEEENK that's what happened...for a couple of reasons: bilge pumps
don't bring water INTO the boat, they remove water FROM the boat...and the
thru-hulls for bilge pumps are above the waterline. So unless there was
already enough water in the boat to put the bilge pump thru-hull under
water, there's no way that a siphon can start in a bilge pump line.

The water that sank your cousin's boat had to be coming in somewhere
else...and either the bilge pumps clogged and failed, or they kept pumping
till they drained the batteries and died...allowing the boat to fill up
and sink. Or, the water was coming in faster than the bilge pumps could
keep up with it. Or any combination/all of the above.

--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://www.seaworthy.com/store/custo...0&cat=6&page=1
http://shop.sailboatowners.com/books...ku=90&cat=1304

Bryan wrote:
Trying to tell people to install vented loops is like trying to get them to
close seacocks when they leave the boat for extended periods. Ain't gonna
happen.


Yep. And that's why somany boats are in the shape they're in.


When you tell people they should close all the through hulls prior to
leaving they say that is not what they are for, or that would take to long,
or don't you trust your hoses, or I can't get too my through hulls,,,,and
that is why most boats sink at the dock.


Yep again. "That's not what they're for"??!? Gee what are
they for then?

"Can't get to my thru-hulls"?!?!!?!!!???!! Why did you buy a
freekin' boat with inaccessible thru-hulls?

Another common one is people who don't know where their
thru-hulls are.


You should see the looks I get from the yard when I tell them the ignition
key is hanging on the closed raw water engine intake and they will need to
open the intake when getting the key to start the engine.


Another goody is people not closing their fuel tank valves.



Gary wrote:
Yup, my cousins bilge pump started syphoning and sank his boat.

"Peggie Hall" wrote
I don' TEEENK that's what happened...for a couple of reasons: bilge pumps
don't bring water INTO the boat, they remove water FROM the boat...and the
thru-hulls for bilge pumps are above the waterline.

Umm, not all of them are.


The water that sank your cousin's boat had to be coming in somewhere
else...and either the bilge pumps clogged and failed, or they kept pumping
till they drained the batteries and died...allowing the boat to fill up
and sink. Or, the water was coming in faster than the bilge pumps could
keep up with it. Or any combination/all of the above.


Rainwater can do it. Also if shore water supply is left
hooked up, and a leak begins (or a hose blows out); that is
a very common way boats sink at the dock (accoring to
insurance). I guess leaving shore water hooked up goes on
the list with leaving thru-hulls & fuel valves open....

Fresh Breezes- Doug King

DSK wrote:
Bryan wrote:

Trying to tell people to install vented loops is like trying to get
them to close seacocks when they leave the boat for extended periods.
Ain't gonna happen.


Yep. And that's why somany boats are in the shape they're in.


When you tell people they should close all the through hulls prior to
leaving they say that is not what they are for, or that would take to
long, or don't you trust your hoses, or I can't get too my through
hulls,,,,and that is why most boats sink at the dock.


Yep again. "That's not what they're for"??!? Gee what are they for then?

"Can't get to my thru-hulls"?!?!!?!!!???!! Why did you buy a freekin'
boat with inaccessible thru-hulls?

Another common one is people who don't know where their thru-hulls are.


You should see the looks I get from the yard when I tell them the
ignition key is hanging on the closed raw water engine intake and they
will need to open the intake when getting the key to start the engine.


Another goody is people not closing their fuel tank valves.



Gary wrote:

Yup, my cousins bilge pump started syphoning and sank his boat.


"Peggie Hall" wrote

I don' TEEENK that's what happened...for a couple of reasons: bilge
pumps don't bring water INTO the boat, they remove water FROM the
boat...and the thru-hulls for bilge pumps are above the waterline.


Umm, not all of them are.


The water that sank your cousin's boat had to be coming in somewhere
else...and either the bilge pumps clogged and failed, or they kept
pumping till they drained the batteries and died...allowing the boat
to fill up and sink. Or, the water was coming in faster than the
bilge pumps could keep up with it. Or any combination/all of the above.


Rainwater can do it. Also if shore water supply is left hooked up, and a
leak begins (or a hose blows out); that is a very common way boats sink
at the dock (accoring to insurance). I guess leaving shore water hooked
up goes on the list with leaving thru-hulls & fuel valves open....

Fresh Breezes- Doug King

I didn't conduct an investigation. His boat sank, it had a bilge pump,
no head, and an outboard. The only thru hull was the bilge pump outlet.
It's his story. Argue about something else.